The disposition of several retinoids in mice and the effects that phenobarbital and 3-methylcholanthrene induction may have on disposition are being investigated. The distribution of all-trans- and 13-cis-retinoic acids has thus far been examined using reversed-phase HPLC analysis of tissue extracts from orally dosed, uninduced mice. Serum levels of all-trans-retinoic acid reached a maximum within 45 min after dosing (10 mg/kg) then declined in a linear fashion. Tissue levels reached a maximum within 30-120 min then declined exponentially with t 1/2 values of 25 to 68 min. The longest t 1/2 value was observed in brain. Only small amounts of all-trans-retinoic acid were observed in bile and feces and none was found in urine. Polar metabolites, however, were present in bile, feces, and urine. Approximately 30% of the total dose administered was eventually excreted in the urine and 70% in the feces, all of which was recovered as polar metabolites. Administered 13-cis-retinoic acid was both more rapidly distributed into the tissues than was all-trans-retinoic acid, and cleared (t 1/2 values of 15-20 min). Very little 13-cis-retinoic acid appeared in bile and none appeared in urine. Efforts in the coming year will be directed at determining the disposition of orally administered N-hydroxyethylretinamide in uninduced mice and all-trans- and 13-cis-retinoic acid in phenobarbital and 3-methylcholanthrene-induced mice.